Firefox Community Forum

I use Firefox with DuckDuckGo on Ubuntu 24.04, Gnome desktop. My Firefox browser window regularly freezes but can be unfrozen by simply repositioning the window. This is really annoying.

I also use Chromium on the same system and there are no issues.

Any ideas?

This started happening a few days ago.

I tried to drag a tab out of the main window to put it in its own window on my other monitor, but the tab just became unselectable, and if i scrolled in the tab bar, the tab icon and text would remain locked in place in the display while the other tabs moved behind it.

The main Firefox window also lost the minimize, restore, and close buttons. The only way to make the tabs work was to close Firefox and relaunch it.

I noticed this happened only after any app in the OS went full screen, be it a steam game, or another Firefox window, or a VLC window, or anything else that I did that made an app full screen in any of my monitors.

I am using Ubuntu 24.04 with KDE Plasma 5.27.12. Kernel is 6.14.0-29. Display server is Wayland.

Initially I thought this could be a problem with the snap version of Firefox, so now I've installed the deb package, but the problem remains. Firefox is the only app which presents a problem of any kind when any window goes full screen.

Here's a video showing what the problem looks like, in case my description was not clear. The ghostly tab in this video is the chess.com home page and you can see it as the third tab from the top right of the video, and it remains in that position as i scroll the other tabs, completely unselectable with the mouse.

https://www.youtube.com/watch?v=-mAfPS3_qkg

Any idea of what could be causing this issue to appear?

Thank you!

This is happening more frequently. sometimes clicking links works but the cursor will not respond if i hover over the new tab button. To continue I have to select a new firefox window, The unresponsive window remains in error even when a new working window is active.

Ubuntu - I use the SNAP version of Firefox - I generally have lots of tabs open but only use 5 or so of them and it's generally fine.... but when I am closing Firefox, it USES like 100% of the CPU and ALL of the RAM and ALL of the SWAP memory when closing.

This locks up the computer.

Sometimes it doesn't quite go all the way but I can watch it all happen in real time, using Task Manager - and that shows a solidwall of all resources occouring, when the close Firefox is run.

I am told by research via ChatGPT that this is a very real problem with the SNAP version and it's best to change to the Debian version, copy all the bookmarks etc., across and then uninstall the SNAP version.

It's rather disconcerting to have Linux crash because of this one app locking it up and frequently.

Chat GPT:

Is there a problem with Firefox Snap Version closing and using all the resources while doing so, which results in locking up the computer?

You're definitely not imagining it—there have been reports of Firefox's Snap version consuming excessive system resources (CPU, memory) and even causing lockups or hangs, particularly during closure. Here's what’s going on and how to mitigate it:

What’s Happening with Firefox Snap?

2. Browser Hangs or Locks the System on Close

On Linux (especially Ubuntu), users have reported that closing Firefox can lead to it hanging in memory, sometimes unresponsive and still consuming resources.
Super User
Ask Ubuntu
A stark example from Reddit illustrates the severity:
“About 50% of the time I open Firefox, it'll reach 100% CPU usage in about 30 seconds… PC completely unusable unless I shutdown.”
Reddit

3. Known Wayland Sway Bug

On Wayland/Sway setups, reloading Sway while Firefox is open can trigger intense logging, causing high CPU use and an enormous syslog.
Fix: Set MOZ_DISABLE_WAYLAND_PROXY=1, or upgrade to FF 125 where the issue is addressed.
Reddit+1

Alternative Approach

Many users, particularly on Ubuntu, opt out of Snap completely in favor of the .deb package or PPA builds. These alternatives often avoid these specific issues. Ask Ubuntu Reddit

Thoughts? Solutions?

Thanks in advance.

• • Background:**

I'm a senior software engineer running Firefox Developer Edition on a Linux machine with 8GB RAM. I have Fission architecture (site isolation) enabled, which I understand is now the default since Firefox 95+.

• • The problem:**

When I open 20 or more tabs across different domains, Firefox's memory consumption scales dramatically — often reaching 4–6GB of RAM for what should be lightweight browsing sessions. This is significantly higher than what I observed before Fission was enabled.

• • What I've already tried:**

- Disabled hardware acceleration → no significant improvement - Set browser.tabs.unloadOnLowMemory to true → partial relief

 but tabs reload constantly, disrupting workflow

- Reduced content.notify.interval → marginal improvement - Tested with all extensions disabled (safe mode) → RAM usage

 still high, confirming it's not extension-related

- Checked about:memory → large number of separate

 "Web Content" processes, one per origin as expected with Fission

• • What I'm trying to understand:**

1. Is there a way to set a maximum process count cap for Fission

  without fully disabling site isolation? I found 
  dom.ipc.processCount but changing it doesn't seem to affect 
  Fission's per-origin process spawning behavior.

2. Is browser.tabs.min-warm-process-count a relevant setting here

  and what is the safe range to modify it?

3. Does Firefox have a built-in memory pressure threshold where

  it automatically consolidates processes — similar to Chrome's 
  memory saver — and if so, which about:config keys control it?

• • Environment:**

- Firefox Developer Edition 151.0b10 - OS: Ubuntu 24.04 LTS - RAM: 8GB - Fission enabled: confirmed via about:support - Extensions: disabled for testing

When I have multiple tabs open, around the 6th tab, the entire computer freezes. I have to press the physical button to shut down and restart. This behavior started with the last Firefox update. It doesn't happen when I use Brave browser. What changed to cause this?

I'm running Mozilla Firefox for Linux Mint mint 100 - 1.0 version 141.0.3 (64 bit) on Linux Mint 22.1 Cinnamon. These are the latest versions of Mint and of Firefox for Mint.

suse linux 15.6 firefox 140.9.0esr (64-bit)

An aggressive website can cause "isolated web co" processes to be started. When they hog all processors and memory, the computer besomes unresponsive. Keyboard and mouse freezes up.

Is there a way to limit firefox processes to n-1 processors, leaving 1 processor available for me to kill it ?

Kubuntu 24.04 with various Firefox iterations including 149.0.2. It happens on stand alone, snap and flatpak versions. I do not know what triggers this problem. As far as can tell it only occurs on Wayland and not on 'X'. .... After using Firefox normally for a while I first notice the problem when I can't click into the separate search box on the toolbar, then I find I can't drag the tabs around as per usual. Then, if I click on a toolbar icon it does not respond. In summary, the toolbar becomes inoperative. I do have 9 pinned tabs but I can often have many more standard tabs up before I ever notice the problem and, today, when it occurred I only had 3 additional tabs up. So, I can't tie the problem to the number of tabs.

What's wrong with the new release?

Today i decided try the new firefox(140) since it's going to be ESR, but i'm getting hot-fan from a couple of tabs (particularly video streams). Second it's slower and seems to have 4second delay for shutdown..

The laptop is running linux mint with intel i5 (11th), tigerlake (iris xe) gpu. It might not be newest, but it shouldn't have a problem with regular web browsing.

Is it a bug? like it's not maxing my ram or cpu during use.

FIREFOX ... MMMMMMMMMMMMMMMMOOOOOOOOOOOOOOOOORRRRRRRRREEEEEEEEEEE THAN 16 GIGABYTES WITH ONLY 4 TABS OPENED. AND OF COURSE .... BROWSER FREEZES, NEED TO KILL FIREFOX TO STAR WORKING AGAIN ....

WHAT ARE YOU SMOKING THESE DAYS?

My Dell Precision Laptop from 2019 runs a frequently updated Ubuntu 24.04. About one or two weeks ago, after one of the latest Firefox updates, i noticed that video streaming produces rectangular flickering in rapid sweeps. ( Also fast scrolling large text websites produces similar flickering, I think I would have noticed it before...) . If you detected it once, you see it always again... :-( First I fiddled around with the nvidia settings because the driver was also recently updated, without much success. Playing locally stored videos, e.g. with VLC media player, still works fine, so the nvidia driver is not the problem i think. Yesterday I installed Chromium and the video performance is fine! As good as with firefox some weeks ago! So it must be one of the latest updates, that causes the problem. Generally I like firefox more than chromium. I like the control you have, e.g. via Add ons.. So I hope that the firefox performance will increase again... Thank you for firefox! Florian Mengedoht

On updating to linux mint 22.3 - cannot type anything in firefox in address box, search and primary password or anywhere else within firefox - have uninstalled & reinstalled but nothing happens

After the version 149, a very strange issue happens to me with Firefox. When I try to log in to some services (Google account, WhatsApp, Mozilla account) the browser freezes. That does not happen if I turn the hardware acceleration off so I essentially thought there is some issue with my graphics drivers which I then updated (Nvidia 580.142 drivers for Geforce GTX 960). But what is very strange is that the issue isn't present when I use Firefox in private mode! That means: Normal mode, HW acceleration on -- freezing Normal mode, HW acceleration off -- not freezing Private mode, HW acceleration on -- not freezing I switched to the ESR version now which works fine too. Still, I am curious about what is going on and I would like to find a solution. My system is fully updated Arch Linux. I cannot share my data since I can't log in to my Mozilla account. Thanks in advance!